Inverse-vulcanization of vinyl functionalized covalent organic frameworks as efficient cathode materials for Li-S batteries

Covalent organic frameworks (COFs) are an emerging class of crystalline porous materials featuring pre-designable structures and tailor-made functions. Herein, a mesoporous imine COF with densely arranged reactive vinyl groups (COF-V) was inverse-vulcanized with sulfur and used as a cathode material for Li-S batteries. Owing to the synergetic chemical covalent binding with the vinyl groups and physical confinement by the mesoporous channels, the shuttle effect of polysulfides could be efficiently suppressed. As a result, the inverse-vulcanized S-COF-V cathode demonstrated a high initial capacity of 1400 mA h g(-1) which retained 959 mA h g(-1) after 100 cycles at 0.2C and can be further cycled 1000 times at 1C with a low fading rate of 0.057% per cycle. These results are among the best performances of reported COF-based sulfur cathodes. Our findings provide a new approach to develop efficient cathode materials for Li-S batteries.